Can you get under the dash and take a picture of how the cable meets up with the quadrant? Something is not right if the cable is coming up short.
I'm also having a hard time seeing why it would be difficult to get a wrench on those nuts. Could you take another picture of the fork where it meets the cable from an angle that looks toward the front of the car? Maybe get the wrench in there to show us why it's a problem.
I use a socket wrench on the nut and a box end wrench on the hex shaped part where the threaded end of the cable and the cable meet.
